Deterioration assessment of an immersed-tube road tunnel in Taiwan

Taiwan has been constructing tunnels since the 1960s and more than 300 are now in operation. Unfortunately, some of the early tunnels are now showing signs of significant deterioration. This paper provides a case study of a busy 30-year-old urban undersea immersed-tube road tunnel, which is suffering from cracks, water ingress and corrosion. Non-destructive inspection techniques were carried out to determine the level of deterioration and to make an overall assessment of the tunnel’s operational safety. The paper describes the tunnel’s main defects, the results of settlement, and the structural inspections and monitoring judgements made. The paper is intended to serve as a reference for assessing the deterioration of immersed-tube tunnels.